Chemistry Reference
In-Depth Information
FIGURE 8.19
CVof a glassy carbon disk electrode modifiedwith a filmof
37
inH
2
O/LiClO
4
.
at a less negative potential, diminishing interferences, and with higher sensitivity than
bare electrodes. The steady-state current due to oxygen reduction decreases as the
glucose concentration increases. The sensitivities obtained are in agreement with the
variation of the electrocatalytic efficiency of the respective electrodes. On other hand,
it was observed that the addition, under aerobic conditions, of the same amounts of
glucose produces similar variations in the oxygen concentrations in all sensors
prepared with similar coverages of the different dendrimers. This fact demonstrates
that the amount of active enzyme immobilized is nearly the same in these sensors.
8.3.2.2 Polymethylferrocenyl Dendrimers We have reported the use of DAB-
based dendrimers as core to prepare a polymethylferrocenyl dendrimers family
(Scheme 8.3) [40]. While macromolecules containing ferrocenyl moieties are nu-
merous, dendrimers and polymers constructed with permethylferrocenyl units have
been relatively less explored. As a result of the enhanced electron donating ability of
permethylated cyclopentadienyl rings, polymethylferrocenyl derivatives have lower
redox potentials. It is also known that modification of the cyclopentadienyl ligand
with methyl substituents causes changes in the rate of the electron transfer [115,116].
In addition, it has been reported that 1,1
0
dimethylferrocene reoxidises GOx at a rate
nearly three times higher than the unsubstituted ferrocene. This improved ability is
maintained after covalent attaching to a siloxane polymer. These are important factors
when these permethylferrocenyl compounds are used as mediators for biosensors to
increase their efficiency andminimize interferences. The electrocatalytical properties
of dendrimers
deposited onto platinum electrodes examined by CV
show that the modified electrodes act as electrocatalysts in either oxidation or
reduction of H
2
O
2
. Amperometric enzyme electrodes based on GOx were employed
for the determination of glucose under aerobic conditions. The enzyme was
21, 22,
and
24
